Bumper assemblies for vehicles may have a stiffness determined by the material and structure of the assembly. The desired stiffness of the bumper assembly may be different depending on vehicle speed. For example, at a low vehicle speed, a higher stiffness may be desired to prevent damage to the vehicle. At a high vehicle speed, a lower stiffness may be desired to absorb energy during a pedestrian impact.
Vehicle research organizations release test protocols and standards for vehicles directed to specific outcomes. For example, the National Highway Traffic Safety Administration (NHTSA) releases the Federal Motor Vehicle Safety Standards (FMVSS), including Part 581, which describes impact test protocols for low speed damageability (“LSD”) of vehicle bumper systems. The test measures damage to a vehicle at low speeds. As another example, the Euro New Car Assessment Program (NCAP) releases Global Technical Regulations (GTR), including GTR 9, which measures pedestrian protection. Specifically, the test measures impact on legs of a pedestrian during a front-end vehicle impact, e.g., at speeds greater than 30 KPH. The requirements for LSD and pedestrian protection may result in competing, and counteractive, design concerns.
There remains an opportunity to design a vehicle bumper assembly that accounts for both low speed damageability and pedestrian impact.